Microfluidic Flow Sensor Thermal Integration

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Solution Overview

Problem

Conventional fluid flow sensors are bulky and expensive, making them difficult to integrate into microfluidic devices and chips.

Innovation Solution

A compact microfluidic flow sensing system that includes a heat emitting resistor integrated within a microfluidic channel, where the resistor's electrical resistance varies with fluid flow, allowing for accurate fluid flow measurement using an electrical parameter sensor and electronics to estimate flow rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional fluid flow sensors are used, then accurate flow measurement can be achieved, but the sensors become bulky and expensive, making them difficult to integrate into microfluidic devices

Engineering Contradiction:

Improveflow measurement accuracyVSAvoidsensor size and integration difficulty

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the flow sensing function with the existing microfluidic channel structure by integrating a heating element and temperature sensor directly into the channel. This merging of functions eliminates the need for separate bulky sensors, achieving compact integration while maintaining measurement accuracy through temperature-based flow detection.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces conventional mechanical or optical flow sensors with a thermal-based sensing system. By using a heating element and temperature sensor to detect flow through thermal convection effects, the system achieves accurate flow measurement without the bulk and complexity of traditional mechanical or optical sensing mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If conventional fluid flow sensors are used, then accurate flow measurement can be achieved, but the sensors become expensive

Engineering Contradiction:

Improveflow measurement accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent makes the microfluidic channel itself serve multiple functions: fluid transport, heating, and temperature sensing. By utilizing the channel structure for flow sensing through thermal effects, the system eliminates the need for separate expensive sensing components, reducing overall device cost while maintaining measurement capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent employs inexpensive thermal sensing elements and heating resistors that can be directly fabricated within the microfluidic channel using standard semiconductor manufacturing techniques. These simple thermal components replace expensive conventional flow sensors, significantly reducing manufacturing cost while providing sufficient measurement accuracy for the application.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Device complexity

If a heating element is used to sense flow, then compact integration is achieved, but power consumption increases

Engineering Contradiction:

Improvesensor size and integrationVSAvoidpower consumption

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent employs periodic or pulsed heating rather than continuous heating to sense flow. By applying heating in intermittent cycles and measuring temperature changes during off-periods, the system achieves effective flow detection while significantly reducing average power consumption compared to continuous operation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses partial heating - only heating the specific region where flow sensing is needed, and only for the duration necessary to detect flow changes. This partial action approach minimizes overall energy consumption while still providing sufficient thermal signal for accurate flow measurement.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables cost-effective and compact integration of fluid flow sensing within microfluidic devices, providing accurate fluid flow measurements with reduced power consumption and enhanced sensitivity.

Implementation Method 1

heat emitting resistor (30) that produces heat and has an electrical parameter that varies in response to the rate at which the produced heat is carried away by fluid flow

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the electrical resistance of heat emitting resistor (30) varies in response to temperature

Methodology Applied

Scientific EffectElectrical resistance variation with temperature: Electrical Resistance

Data Source

PatentUS10655994B2Microfluidic flow sensor

Publication Date: 2020.05.19 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

An apparatus includes a microfluidic channel and a flow sensor along the microfluidic channel. The flow sensor includes a heat emitting resistor for connection to an electric current source, analytical parameter sensor and electronics. The heat emitting resistor has a resistance that varies in response to temperature. The electrical parameter sensor is to sense an electrical parameter of the heat emitting resistor that is based on the resistance of the heat emitting resistor. The electronics determine a flow based on the sensed electrical parameter.